I can understand that perspective, especially from a noncommercial perspective. As a restaurant manager, I can guarantee you that the costs are orders of magnitude apart at a larger scale. Semolina is much cheaper than parchment.
Parchment paper really helps if you're making multiple pizzas, too. You can roll out each crust and assemble the toppings and then keep them all on a table (without a bunch of flour) ready to go into the oven.